strstr.c   [plain text]

/*
 * strstr.c -- return the offset of one string within another.
 *
 * Copyright (C) 1997 Free Software Foundation, Inc. 
 *
 * This program is free software; you can redistribute it and/or modify it under
 * the terms of the GNU General Public License as published by the Free
 * Software Foundation; either version 2, or (at your option) any later
 * version. 
 *
 * This program is distributed in the hope that it will be useful, but WITHOUT
 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
 * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License for
 * more details. 
 *
 * You should have received a copy of the GNU General Public License along with
 * this program; if not, write to the Free Software Foundation, Inc., 59
 * Temple Place - Suite 330, Boston, MA 02111-1307, USA.  
 */

/* Written by Philippe De Muyter <phdm@info.ucl.ac.be>.  */

/*
 * NAME 
 *
 * strstr -- locate first occurence of a substring 
 *
 * SYNOPSIS 
 *
 * char *strstr (char *s1, char *s2) 
 *
 * DESCRIPTION 
 *
 * Locates the first occurence in the string pointed to by S1 of the string
 * pointed to by S2.  Returns a pointer to the substring found, or a NULL
 * pointer if not found.  If S2 points to a string with zero length, the
 * function returns S1. 
 *
 * BUGS 
 *
 */

char *
strstr (buf, sub)
     register char *buf;
     register char *sub;
{
  register char *bp;

  if (!*sub)
    return buf;
  for (;;)
    {
      if (!*buf)
	break;
      bp = buf;
      for (;;)
	{
	  if (!*sub)
	    return buf;
	  if (*bp++ != *sub++)
	    break;
	}
      sub -= (unsigned long) bp;
      sub += (unsigned long) buf;
      buf += 1;
    }
  return 0;
}